Inactivation of DNA adenine methyltransferase alters virulence factors in Actinobacillus actinomycetemcomitans

Abstract

DNA adenine methyltransferase (DAM) plays critical roles in diverse biological pathways in gram-negative bacteria, and specifically in regulating the expression of virulence genes in several organisms. Actinobacillus actinomycetemcomitans plays an important role in the pathogenesis of juvenile and adult periodontal disease, yet little is known about its mechanisms of gene regulation. DAM is shown here to directly or indirectly affect well-known A. actinomycetemcomitans virulence factors. A mutant A. actinomycetemcomitans strain lacking the dam gene was created by homologous recombination and shows normal growth phenotypes when grown exponentially. This mutant strain has four sixfold increased levels of extracellular leukotoxin, altered cellular levels of leukotoxin, and significant changes in bacterial invasion of KB oral epithelial cells. These results provide a basis for further characterization of regulatory mechanisms that control A. actinomycetemcomitans virulence.

Roles of DNA adenine methylation in host–pathogen interactions: mismatch repair, transcriptional regulation, and more

“…Furthermore, A. actinomycetemcomitans dam mutants show reduced invasion of epithelial cells (Wu et al , 2006). …”

Differential epithelial cell response upon stimulation with theAggregatibacter actinomycetemcomitansstrains VT 1169, VT 1560 DAM-and ATCC 4318

“…19 The present study indicated that the DAM-deficient strain VT 1560 showed the reduced capacity to induce hBD-2 and IL-8 by trend compared to the native strain, which may be related to a reduction in virulence of this mutant. Wu et al 19 discussed that the observed invasion deficiency was based on an adhesion deficiency rather than on a change in the ability to invade, which is in accordance to the present observations that could be a result of reduced interactions between biofilms and epithelial cells.…”

“…Single-species biofilms were grown in a stationary biofilm forming system modified from Guggenheim et al 28 The following strains of A. actinomycetemcomitans were investigated: Y4 (ATCC 43718), VT 1169 a derivate of SUNY 465 and VT 1560 the DAM knockout strain cloned from VT 1169. 19 The parent strain (VT1169) is a spontaneous rifampinnalidixic acid resistant derivate of a smooth-phenotype A. actinomycetemcomitans strain (SUNY 465). 30 The strain ATCC 43718 is a spontaneous smooth-colony variant of the respective clinical strain.…”

“…17 A DAM-deficient mutant of A. actinomycetemcomitans showed increased levels of extracellular leukotoxin and the reduced capacity to invade epithelial cells. 19 On various epithelial surfaces as well as in the oral cavity structured bacterial biofilms can be pathogenic and induce chemical defense mechanisms or inflammatory responses in epithelial cells. Biofilms consist of multiple different microorganisms living in a structured ecosystem that protects bacteria from microbicidal host defense.…”

Epigenetics and periodontal disease: future perspectives

“…The DNA adenine methyltransferase (DAM) has been identified in oral bacteria and represents an important role in the control of the expression of virulent genes. Wu et al [42] reported that DAM-mediated methylation may regulate genes required for the invasion process of A. actinomycetemcomitans.…”